Apparatus for feeding and automatically weighing the gross weight of material fed into a bag or similar container are old and well-known in the art. Basically two types of conventional weighing units have been available for many years, one wholly mechanical and the other a fully automatic digital scale.
The mechanical version utilizes a hand lever to manually open the feed gate. The hand lever is held open by a trigger and latch mechanism. As the material flows into the bag, it is measured by a conventional pivoted beam and counterweight scale. Upon reaching a certain gross weight, a mechanical arm is contacted by an adjustable bolt on the scale beam which unlatches the hand lever to return to the closed position to close the feed gate.
In the fully automated, digital version of this type of apparatus, an air piston and cylinder arrangement operates the opening and closing of the feed gate. A conventional load cell and digital control means function to weigh the material fed into the bag, and at a set weight, energizes a solenoid to actuate the piston to close the gate.
It is generally well recognized in the trade that the digital scale arrangement is more accurate, reliable and convenient to use than the fully mechanical version. However, the very significant disadvantage of the present digital scale system is the dramatic increase in cost of such units compared to the mechanical bagging scales.
This high cost is particularly significant to the smaller business which has purchased and has been gainfully using a mechanical system. Replacement of an existing presently available mechanical system with automated digital unit represents an investment of several thousands of dollars. It is a reasonable estimate that over ten thousand of these mechanical bagging scales are presently in use. The useful life of a large majority of these scales has not been exhausted, therefore many users are reluctant to make the significant expenditure necessary to purchase the costly automated digital bagging scale with its attendant advantages over the mechanical version.
Therefore there has been an unsolved need for many years to provide an upgraded scale system which achieves the most important advantages of the automated digital systems without incurring the dramatic costs associated therewith and to make economic use of the existing mechanical versions presently in use.